Download Plant Species Suitability For Restoration

Plant Species Suitability For
Restoration
Adapted from "A study of plant materials suitable for use in watershed and wildlife habitat improvement in the Trinity
River watershed, California." 1990 by Stephen Matthews, Michael J. Furniss, and Tom Leskiw. Call Steve
Matthews at (707) 441-3650 to request a copy.
The following is the types of information that should be considered to determine the suitability of plant species for
revegetation projects. Ideally, the best plant to use for revegetation would be a native that reliably produces easy-tocollect seed, is easy to grow in suitable quantities, is easy to handle, is environmentally adapted, with a root system
that is strong and capable of rapidly stabilizing soil. It would provide food, cover and nesting habitat for wildlife and,
in addition, would not have any allelopathic or inhibitory effect on other desirable plant species that invade later but
instead would facilitate the natural recolonization of the site by native species adjacent to the site while keeping out
other undesirable "weed" type plants. Unfortunately, there are few if any species that meet all of these criteria. It
may also be ironic that some non-natives may meet more of these requirements than native species.
The suitability of a species for use in revegetation projects varies considerably depending on a number of factors. A
species that is suitable for one site may be unsuitable for many other sites depending on the conditions of the site
and the goals of the project. The following is a list of some of the factors that may affect suitability with a short
discussion each.
Preferred site - It is usually best to use a species that is the most environmentally adapted to the site. In some
instances however, it may be necessary or desirable to use a species that is not ideally adapted. An example of this
would be a species that can survive just long enough for the local native species to colonize the site.
Native Community - The native plant community that the plant occurs in is a clue to its adaptation and the kinds
of environments where it may thrive. A strategy of using plants that occur in plant communities that are adjacent to
planting sites may be ecologically most prudent, and integrates a variety of ecological considerations.
Native species - Native species were defined as species that are known to occur naturally (not introduced) in
northwest California. All species in this report are native unless noted.
Non-native naturalized species - Non-native naturalized species were defined as species that were introduced by
man to northwest California and have become naturalized or a part of the natural communities.
Non-native exotic species - Non-native exotic species were defined as species that are not known to occur in
northwest California except possibly in landscape plantings or botanical gardens. Native species are preferable to
non-native species for use in revegetation projects. If a non-native species is being considered, a good rule to
remember is that the species should in a sense act as a semipermeable membrane, letting desirable native species
gradually recolonize the site while holding the soil and shutting the door on noxious weed invasion. The introduction
of non-native species may lead to unanticipated adverse consequences on the surrounding flora by the displacement
of native species or changing native species genetic and physical caution should be used when selecting non-native
species for revegetation projects. A good discussion of the use of native vs. non-native species may be found in Millar
and Libbey (1989).
Range - Includes information on the species natural range or distribution. This information would be useful for
determining species adaptability.
Nitrogen-fixing species - Nitrogen-fixing species are generally essential for adding nitrogen and building soils on
landslides or other disturbed areas that have shallow or undeveloped soils. Most nitrogen-fixing species require
innoculation and may benefit from phosphorous fertilization. Innoculation involves the introduction of the specific
nitrogen-fixing bacteria to the roots or seed of the plant before planting. One common practice is to collect and use
the soil duff or litter adjacent to the same species growing in the field to inoculate the roots or seed before planting.
Habit - All species were grouped by whether they are a tree, tall shrub 5 ft.), medium shrub (> 2 ft. & 5 ft.), low
shrub ( 2 ft.), forb or grass. This information would be useful for selecting species that meet specific vegetation
height or cover requirements. Other information provided includes whether species are deciduous or evergreen,
information on species flammability and other information that may influence species selection.
Deciduous vs. evergreen - Deciduous species may provide more organic matter to the soil and have higher soil
building capability than evergreen species. The leaves of deciduous species also provide food for fish indirectly by
providing food and habitat for insects along streams or rivers.
Growth - Includes information on growth rate, invasiveness, dissemination, etc.
Growth rate - Growth rate may be important where rapid vegetation establishment is desired. Rapid growing
species are generally shorter lived however.
Invasiveness - Invasive species are generally not desirable for use in revegetation projects. The ideal species is one
that is easy to establish but is non-invasive and will allow the eventual colonization of native species adjacent to the
site.
Roots - Includes information on root depth, structure and strength. Deep-rooted woody perennial species are
generally more desirable for stabilizing slopes since their root systems provide greater strength for holding soils at
deeper levels. A diffuse, fibrous root system however, is better suited for binding loose sandy soils (e.g., decomposed
granite), retarding gullying and limiting sheet erosion. Perennial vs. annual or biennial - Information on whether the
species is perennial, annual or biennial is important in determining efficacy in erosion control and soil building
effectiveness.
Litter - The kind and persistence of litter production is important for erosion control and soil building. Long-needled
pine species, for example, drop considerable quantities of persistent needles that interlock and resist wind and
gravity. Many decidous species, such as oaks, drop plenty of litter, but it can easily blow away from the treatment
site. The allelopathic properties may also be a crucial consideraiton.
Erosion control - In most cases, perennial species are preferable to annual or biennial species for long-term erosion
control. With grasses, most annual or biennial species consist of non-natives which are better adapted to lower
elevations below the commercial forest zone. The use of annual or biennial grass species at lower elevations,
however, can result in a dense, self-reseeding, difficult-to-control grass cover that strongly competes with conifer
seedlings for soil water and can promote fire control problems. For these reasons, annual and biennial grass species
are generally better suited for erosion control at higher elevations where they are less adapted and less likely to
prevent establishment of more desirable perennial shrub or tree species.
Soil building - Short-lived species generally provide more organic matter above and below ground than longer-lived
species.
Disease - Includes information on whether the species is susceptible to disease or acts as a host for disease
transmittal.
Reference
Millar, C.I. and W.J. Libby 1989 Restoration: Disneyland or a native ecosystem: A question of genetics" Fremontia,
July 1989.